OK, so the thermistor that rick's diagram says terminates defrost is not the same control as the bimetal? I may have missed it in the diagram but I don't see other leads coming back from this bimetal sensor to the board. or is it just in series with the Def terminal on the AC side rather than the DC control circuit.

and thanks for tip to look at location of resistors to identify different board.

there was definitely something cooked on the original board when I changed it and I left it sitting on my bench for 2 years in the box from the replacement board but can i find it today . . . nooooooo.

I didn't do the second replacement.

I think this thread was just starting up back then when I did the first and wish I had found it then because I would have had a better chance of tracing the cause.

Yes I understand power spikes are a problem generally although not really a believer that current surge technology can quench lightening level problems without damage to sensitive electronics although I think instability and switching on the grid can be controlled for.

But no other damage to electronics in this building and it returns me to my concern about having this stuff digitally controlled to begin with.

thanks, headed over there to have a look right now. Might have a little more info next time I post.

The evaporator thermistor controls when the unit comes out of defrost, unlock most refrigerators it is not controlled by the TOD, the TOD is used only as liner protection. If the thermistor fails that's a safety device.

The TOD is a line voltage device used as an over-temperature limit. It is wired in series with the defrost heater. The door openings, evaporator thermisters, compressor run-time, are all inputs to the adaptive defrost system which initiates and terminates the defrost cycle. The TOD is a safety to keep from having the heater run wild if something fails in the control circuit, nothing more. I retired as Electrical Foreman at a University with over thirty million dollars of equipment in the Public Television and Public Radio studios and another twenty million dollars worth of stand alone electronic equipment. I can assure you that surge suppression works very well. Obviously, the better it is the more expensive it is. But even the cheap ones are a thousand times better than nothing at all.Sq-D and GE and other panel manufacturers make residential surge suppressors for their breaker panels. They cost under $200 installed, and come with a $50,000 warranty. As an electrical contractor in an area with a lot of lightning, I sell a lot of them. We tell the customers to contact us if they have any failures during a thunder storm or power outage and we will file the claim. In 9 years we have yet to have a complaint. They work.

Sorry, I got side tracked on my last post. I forgot to ask: On the two previoius board replacements was it due to a problem with the evap not defrosting, did you replace the board only (no other parts), and did it fix the problem?

yes, first time it was defrost problem. remember that there was some obvious damage to the board and I saved the board but as I said, no can find.

I'm wondering where to look for the onboard wiring diagram on these GE SxS units. I haven't been able to find one, which would have answered my question about the bimetal.

so this is definitely a defrost episode we're having here and not evap fan problem . just saw the fridge. aside from the obvious ice build up in the back of the freeze, getting 13.5 volts J2 pins 3-8 and 12.5 volts J2 pins 3 -4.

I moved the remaining food to another fridge and I'm letting it defrost tonite so I can get at the evaporater, but I'm a little confused as to which two legs I should be ohming at the board to test the defrost circuit itself because the connector that supplies the defrosters and compressor alternatively has a line input and the neutral appears to go to the next connector over. so I don't see any neutral wire to the defrost cycle to ohm against the line out from the 3 pin connector.

board looks fine. no obvious damage or discoloration. maybe it's not the board this time.

but I'm getting infinite ohms across J1 4 to5 which is the evaporater thermister, as well ass across 5 to all the other thermisters which is what is shown in Rick's diagram. I'm wondering if my J1 could be wired differently. and that gets me back to looking for a wiring schematic with color codes. I definitely have the WRX5510942 board that's being dealt with here but can't find a serial number on the fridge. I think it may have been one of those 'refurbs' so unless there is an onboard schematic I'm going to have to find likely model numbers and search for a diagram until I find the one that works.

The resistance will vary inversely with the temperature. At 68 deg F. you will have 6200 ohms; at 32 deg F you will have 16,300 ohms. Of course the plug must be disconnected from the board. Not all meters will read this correctly. Buy some similar resistors at Radio Shack and check your meter. The serial should on the foil nameplate in the upper right side of the refrigerator section. Save this pdf before it's gone: http://www.applianceaid.com/pictools/gefridge1.pdf

OK been in the cabinet today and this has an aftermarket L45-15 bimetal that sits at the very top of the evaporator. seems a little on the cold side. but even the originals are usually labeled so don't figure the guy who was in here last year would have gone too far awol but does anyone know the normal design temps.

anyway, this one ain't easy to trigger so it ain't easy to reclose the switch by dipping in ice water at a 15 setting. I put it all back together and run for a couple hours and it still hasn't closed assuming I'm ohming the right wires. i'm pulling the plugs on the 120 end of the board and testing the orange wire that Rick has labeled neutral on the exteme left hand end of the bigger connector to the blue wire at the center of the 3 pin comp/defrost plug. these wire color codes check out inside the box.

if it isn't reset by tomorrow I'll cut it out and join the wires to make sure I'm testing the right ones and then get another. and i'll get on to seeing if the adaptive defrost seems to be working.

I don't find any way to trigger the card via the controls (no digital controls or address to the card on this one, only a typical temperature dial).

I suppose from reading the description I could open and close the door a bunch of times but I'm not clear that even a lot of that would trigger the defrost without time.

This was some kind of leftover or warranty return fridge because the serial/model number sticker was removed. I can see the glue mark where it was upper right side of the fridge box.

I don't find anything on the back that indicates a model number and haven't located a wiring diagram. don't know where you look on these. I tried looking for an envelope behind the front and back bottom covers, or one glued onto the back cover but no dice.

I did pull the J1 connector when I was getting infinite ohms across the evap thermister but I maybe should have jumped a range or two on the meter.

It was room temp in the box at that time and I think I was on the 2K range and that should have read around 6400 or less according to the stock figures, but maybe it still shows infinite if the ohms are higher than the range. may be my bad on that one. I'll recheck next visit.

They already got another fridge going and I'm just taking this slow and a step at a time. it's right near other jobs and I want to go step by step and help them decide whether to keep fixing this or switch. There is counterdepth frigidaire SxS I can bring in but wonder if that is a good choice or frying pan into fire.

or if not frigidaire whose are most bombproof, easy to diagnose, more modularly replaceable control strategy or . . .